Communication system



K. E. FITCH 2,173,551

COMMUNICATION YSYSTEM Fil'ed Dec. 16, 1957 '7 Sheets-Sheet 1 Sept. 19, 1939.

M D .5E ze H I E o:

7 Sheets-Sheet 2 K. E. FITCH Filed Dec. 16, i937 COMMUNICATION SYSTEM LA/Amm b /NVENTOR /ff F/rcH BygW/Jvrvll-JJ ATTORNEY Sept. 19, 1939.

Sept. 19, 1939. K. E. FITCH COMMUNICATION SYSTEM Filed Dec.16 1937 7 Sheets-Sheet 3 )WX/M ATTOR/VE Y 'SepL- 19, 1939. K. E. FITCH 2,173,551

COMMUNICATION SYSTEM Filed Dec. .16, 1937 7 Sheets-Sheet 4 POL Riina/'23 2 L -illll /N VEN TOR d KEF/TCH 8"; WJM' A 4Tron/VE Y POLAR/IED Sept. 19, 1939. K. E. FITCH COMMUNICATION SYSTEM Filed Dec.` 16, 1957 '7 Sheets-Sheet 5 QUT* /A/VE/vroR KEF/TCH BV J Q ATTORNEY K. E. FITCH COMMUNICATION SYSTEM Sept. 19, 1939.

7 Shets-Sheet 6 Filed Dec. 16, 1937 /NVENTR KEF/TCH llfuwmk.

sept. 1.9, 1939. K. E- FITCH 2,173,551

COMMUNICATION SYSTEM Filed Dec. 146, 1957 7 Sheets-Sheet 7 D/FFE RE N TIAL /NVENTOR KE. F TCH T TORA/E Y Patented Sept. 19, 1939 UNITED STATES PATENT OFFICE COMDIUNICATION SYSTEM Karl E. Fitch, Summit, N. J., assignor to Bell Tele- ;f phone Laboratories, Incorporated, New York,

N. Y., a corporation of New York Application December 16, 1937, Serial No. 180,075

7 Claims.

This Vinvention Vrelates to communication systems and more particularly to telegraph switching systems.

In the past it hasbeen the practice to supervise .5 over the intermediate sections of long multisection subscribers lines by the use of either marking or spacing signals ofv diierent lengths or periods of time. Disconnect, recall, and break signals were distinguished from each other only ,r 10 by their length. With this arrangement the time required to transmit the supervisory signals over the system becomes quite long and the method of operation rather cumbersome. In addition, the equipment is usually set in a particular condition ,15 and remains in that condition until some signal m is received to change the condition.

An object of this invention is to provide supervisory arrangements for long multisection subscribers lines in which ther supervisory signals r* ,20 are transmitted through the system without material delay.

Another object of this invention is to provide a supervisory system for long multisection subscribers lines in which the supervisory signals 25 at each end of the system are continuously controlled from the other end.

A further object of this invention is to provide supervisory arrangements for the intermediate sections of long subscribers line circuits in which 30 it is possible to distinguish between ringing signals, marking current, spacing current, break signals, disconnect signals and recall signals.

Another object of this invention is to provide supervisory signals over the usual well-known 35 types of telegraph circuits. v Another object of this invention is to provide terminal equipment for long multisection subscribers line circuits which cooperate with the switching apparatus at the central exchange in 40 the same manner as local line circuits cooperate therewith.

Another object of this invention is to provide an intermediate supervisory circuit arrangement which cooperates with the same subscribers stav.45 tion circuit and equipment as employed at local subscriber stations.

Another object of this invention is to transmit over a telegraph line arranged to transmit only two signaling conditions all the signals trans- 50 mitted over a connecting line which transmits at least three different signaling conditions.

Another object of this invention is to distinguish between break signals and supervisory signals by transmitting either ringing current or a 55 series of uniform length impulses over the system in at least one direction during break signals and to transmit continuous marking and spacing currents to indicate supervisory signals.

In a preferred embodiment of this invention a multisection subscribers line circuit is provided 6 which employs the same subscriber station circuits and equipment as employed at local subscriber stations. The long line circuit is arranged to cooperate with the switching apparatus or cord circuit at the central station in the same manner l as local subscribers line circuits cooperate therewith. At least one intermediate repeater station is provided between the central exchange and the subscribers station. Between the subscribers station and the intermediate station substantially l the same types of signals are transmitted as are transmitted between the local subscriber station and the central exchange equipment.

Between the central station and the intermediate station one or more sections of a full duplex telegraph channel are provided. Any form of full duplex telegraph channel is suitable including both diiferential and bridge type full duplex circuits arranged for operation over either open wire lines or cable circuits and which employ either a ground return or a full metallic circuit.

In addition, any type of full duplex carrier current channel is suitable for the intermediate section. The carrier current channels may be either of the voice frequency or higher carrier current frequencies and may also include radio channels. Furthermore any suitable or available combination of the various types of full duplex circuits may be employed between the intermediate point and the central exchange. The transmission of 85 break signals in at least one direction over the system is distinguished from supervisory signals by transmitting a series of signal impulses of uniform length over the full duplex channel during the break signal. In the preferred embodiment of this "invention this series of impulses of uniform length is generated by applying alternating current and preferably 20-cycle ringing current to the terminal equipment of the full-duplex channel. The relays of this equipment respond by following the alternations of the applied a1- ternating current and transmit a series of uniform signaling impulses of alternate marking and spacing current of substantially unit length.

These and other objects and features of the invention, the novel features of which are particularly pointed out in the claims appended hereto, may be more fully understood from the following description when read with reference to the attached drawings in which:

Fig. 1 shows the manner in which Figs. 2, 3, 4, 5, 6, '7 and 8 are arranged to form a typical telegraph system embodying the present invention;

Fig. 2 shows the circuit arrangement at the subscribers station;

Fig. 3 shows the circuit arrangement at an intermediate station;

Fig. 4 shows an intermediate line section;

Fig. 5 shows a terminal circuit arrangement at the central exchange which cooperates with the cord circuit;

Fig. 6 shows a circuit arrangement of the cord circuit;

Fig. '7 shows the operators equipment; and

Fig. 8 shows typical local subscribers line circuit and station equipment.

General description In the embodiment of this invention shown in Figs. 2, 3, 4, 5, 6, "I and 8 the line circuit is open at the subscribers station during the idle condition, i. e., when it is not desired to communicate therewith. The line circuit extends from the subscribers station to an intermediate station at which one of the conductors is normally connected to ground and the other to battery. The intermediate sections of the full duplex channel extending between the intermediate station and the central station are normally maintained in the spacing condition in both directions and the circuit is disconnected at the central exchange. When a subscriber desires to originate a call he completes the line circuit at his station. This closure is repeated at the intermediate station by changing the signaling condition transmitted from the intermediate station to the central exchange, from a spacing condition to a marking condition. The marking condition, when received at the central exchange, causes the lamp associated with the subscribers line to light to attract the operators attention.

The operator answers the call by inserting the answering plug in the jack associated with the line circuit. This causes the terminal equipment to transmit a markingr condition from Vthe central exchange to the intermediate station, which vcompletely establishes the transmitting circuits between the subscribers station and the central exchange.

During the transmission of signaling impulses between the subscribers station and the central ofce the various transmitting circuits and systems operate in the usual manner. However, in case a break signal is transmitted from the subscribers station which exceeds the normal length of spacing signals usually encountered in the telegraph signaling combinations ringing current is transmitted from the intermediate point to the central exchange during the remainder of the break signal to differentiate it from a disconnect or recall signal. At the central cnice the nal response to a spacing signal is delayed a short interval. If ringing current is received during this interval, nal response is further delayed during the reception of the ringing current.

An alternating ringing current is employed which has a frequency of 20 cycles. This ringing current passes over the intermediate telegraph lines and circuits as unit impulses of alternate marking and spacing current.

A subscriber transmits a recall signal by momentarily interrupting the line circuit at his station and connecting ground to one of the wires. This causes the equipment at the intermediate station to momentarily transmit a spacing signal over the intermediate sections to the central office. At the central oice the prolonged spacing signal causes the cord circuit supervisory lamp to light, and then ilash if automatic recall is provided, or to relight and then follow the operations of the recall key at the subscribers station. Disconnect signals are transmitted from a subscribers station by opening the line at the subscribers station and connecting ground to one of the line wires. This causes the equipment at the intermediate station to transmit a` spacing current or condition over the intermediate section to the central office. When the prolonged spacing signal is received at the central oice it causes the cord circuit supervisory lamp to light continuously. This indicates to the operator that the subscriber has completed the call, whereupon the operator disconnects by removing the cord from the jack'associated with the subscribers line. This causes a spacing condition to be transmitted from the central eX- change to the intermediate station where itcauses the circuits to return to normal.

When the operator desires to call a subscriber she inserts a calling plug in the jack associated with the subscribers line. This causes the terminal equipment at the central exchange to transmit a marking current to the intermediate station. However, the apparatus at the intermediate station does not respond to the marking current received at this time. The operator then operates the ringing key Aassociated with the.

cord circuit and transmits ringing current to the terminal equipment. The ringing current. is transmitted over the intermediate line sections as alternate marking and spacing impulses of unit length. When these impulses are received at the intermediate point, they cause ringing current to be applied to the line extending to the subscribers station and ring a bell to call a subscriber. The subscriber answers as before and the various circuits operate as described above.

In case it is desired to provide unattended service at the subscriber :station the operator holds the ringing key operated for a prolonged period of approximately nine or ten seconds. This causes a slow relay to operate at the subscribers station equipment after which a message can be transmitted to the subscribers station and recorded by his teletypewriter. During the transmission of the message to the subscribers station the circuits operate as described above. At the completion of the call it is necessary to send a motor stop signal over the system.

` This causes the teletypewriter to close a particular contact which deenergizes the subscribers station motors and other equipment.

Idle condition The idle condition of the relays remain as shown in Fig. 2 except relay 24 which may be in either the position shown or in its right-hand' flowing through the lower winding in a circuit from battery through the lower break contacts of relay 55, through lower winding of relay 58 to ground. Relay 59 may be either in its righthand or left-hand position when the circuit is idle.

The relays of the full duplex section shown in Fig. 4 are maintained in their spacing positions as shown. Relays' 2DI and 283 are maintained in their left-hand positions by an obvious circuit through their lower windings. These relays serve to maintain relay 2I0 at the distant end in its spacing or right-hand position. Relays 2I2 and 2I3 are maintained in the right-hand or spacing position by an obvious circuit through their lower winding and in turn cause relay 208 at the other end of the circuit to be maintained in its lefthand or spacing position. Current flowing through the lower windings of relays 20|, 203, 2 I 2 and 2 I3 maintains them in their spacing position because no current flows through their upper windings at this time.

The relays are shown in Fig. 5 in their normal condition. Relay 232 is maintained in the position shown by current flowing in an obvious circuit through its lower winding. Relay 229 is maintained in its right-hand position by current flowing through its middle winding, in an obvious circuit. Relay 226 is maintained in its marking or left-hand position by current flowing in a circuit from ground through its lower winding and the upper break contacts of relay 221 to battery. Relay 220 is maintained in its spacing or righthand position by current iiowing in a circuit from ground through its lower winding and the marking contacts of relay 226 to negative battery. Relays 225, 22S and 232 are controlled by the current flowing through their lower windings at this time because no current flows through their upper windings. Relay 233 is maintained in its right-hand position by current iiowing in a circuit from ground through its upper winding, upper break contacts of relay 235 and spacing contacts of relay 232 to positive battery. Current flowing through the lower winding of relay 233 in an obvious circuit tends to operate this relay to its left-hand position but is overpowered by the current flowing through the upper winding which holds it in its right-hand position.

'Ihe relays are shown in their normal positions in Figs. 6, '1 and 8. Relays 98 and 9| of Fig. 6 may be in the position shown or in the opposite position.

Subscriber originates a call When a subscriber desires to originate a callhe momentarily operates key 12 to a position where it operates the right-hand contacts. With the right-hand springs I3 of key 'I2 operated, a circuit is completed for the operation of relay 21 from source of power 28 through the winding of relay 27 and the lowermost right-hand springs I3 of key I2 to the grounded side of the source of power 28. Relay 21 in operating completes a locking circuit from source of power 28 through the winding of relay 21, upper contacts lof relay 21, stop contacts I4 of key 12, motor control contacts I5 to ground. Relay 21 in operating also completes an operating circuit for relay I2 from source of power 28 through the lower contacts of relay 21 to ground through the winding of relay I2. Relay 21 in operating also connects source of power to motors 38 and 3l and to the motor generator set 29. Motor generator set 29 causes current to flow through the lower winding of receiving relay 24 which tends to operate this relay to its right-hand position.

The operation of relay I2 and the restoration of key 12, which permits the right-hand springs to return to normal, clos-es the line circuit through the subscribers station.

This causes the operation of relay 49 at the intermediate station (shown in Fig. 3) in a` circuit from battery through the winding of relay 49, the upper break contacts of relay 68, upper: break contacts of relay 5I, line Ill to the subscribers station circuit shown in Fig. 2, the upper operated contacts of relay I2, normal upper contacts of the lower set of contacts of key 12, normal contacts of recall key I6, upper winding of, relay 24, distributor I1, break key I8, transmit- Relay 5I) in operating completes an obvious cir-V cuit for the operation of relay 5I. Relay 5I operating completes a locking circuit from battery through its winding and lower contacts to ground through the break contactsI of relay 10. Relay 5I in operating completes an obvious circuit for the operation of relay 52. Relay 5I in operating also transfers the circuit of lines I and II from ground and relay 49 to the windings of relay 51 and interrupts the operating circuit of relay 49, allowing this relay to release. Relay 49 in releasing interrupts the operating circuit of relay I! which in turn releases.

The subscribers line now extends from negative battery through the lower winding of relay 51, and the upper inner operated contactsI of re-. lay 5I, line II to subscribers station equipment, through contacts of key 12, sending contacts I9, break key I8, tape transmitting distributor I1, upper winding of relay 24, normal contacts of recall key IS, contacts of key 12, upper inner contacts of relay I2, line .I0 to the intermediate station, middle set of upper operated contacts of relay 5 I upper winding of relay 51, upper winding of relay 59, choke coil 69 to the armature and transmitting contacts of relay 58. Current howing in this path through the upper winding of relay 59 causes the armature of this relay to move to its marking contact if it had been resting on its spacing Contact. Current flowing in this line circuit flows through the upper and lower windings of relay 51 in opposite directions so that they neutralize each other and produce substantially no magnetic eiTect upon relay 57. Relay 51 accordingly remains in its normal position.

Current iiowing through the upper winding of relay 24 in this circuit to the subscribers' station causes relay 24 to operate to its left-hand contacts and completes a circuit for the operation of printer magnet 32 from the positive terminal ci motor generator 29, winding of printer mag--` net 32,1eft-hand contacts of relay 24 to the negative terminal of motor-generator 29. Current iiowing through the upper winding of relay 24 is in the opposite direction and overpowers the current flowing through the lower winding of relay 24.

Relay 52 (Fig. 3) in operating, as described above, completes an obvious circuit for the operation of relay 53. Relay 52 in operating also connects ground to the armature and of winding of relay 56. Relay 56 operates to its left-hand position in a circuit from negative battery through the marking contacts of relay 59, winding of relay 55 to ground through the upper inner operated contacts of relay 52. In this position relay 5B completes a circuit for the operation of relay G5 to its right-hand position from battery through the winding of relay 5l), left-hand contacts of relay 53 to ground through the upper outer operated contacts. of relay 52. Relay 52 in operating also interrupts the circuit of the right-hand Contact of relay 53 and transfers the circuit of the left-hand contact of relay 50 to the winding of relay 13. These circuits perform no useful functions at this time.

The operation of relay 53 connects ground to the potentiometer comprising resistance 14 and network 1| and supplies the proper potential to the lower or biasing winding of relay 55. This conditions relay 59 for receiving telegraph signaling impulses from the subscribers station. The operation of relay 53 extends lines |90 and |9| to contacts of relays 55 and 13, respectively and prepares a circuit for the operation of relay 54 from negative battery through the winding of relay 54, upper break contacts of relay 54, upper operated contacts of relay 53, line |93, resistance 206 to negative battery through the spacing contacts of relay 211|. Relay 54, however, does not operate this circuit because negative battery is connected to both of its winding terminals.

However, when relay 53 operated as pointed out above it extended line |9| to the contacts of relay 13. This completed the circuit for operating relays 20| and 203 to the marking positions. This circuit may be traced as follows: From positive battery through resistance 234, upper windings of relays 20|, 203, resistance 285, line 19|, operated lower contacts of relay 53, break contacts of relay 13 to negative battery through the armature and marking contact of relay 59. Current flowing through the upper windings of relays 23| and 233 overpowers the ciurent flowing through the lower windings of these relays and causes these relays to move to their marking positions. The operation of relays 25| and 203 to the marking positions transmits marking current through the noise suppression filter 26|, the upper and lower windings of relay 238, line 261, upper and lower windings of relay 213, noise suppression lter 2|6 through the spacing contacts of relays 2|2, 2|3.

The armature of relay 2|U responds to this marking condition and moves to its marking contact. This causes the operation of relay 232 of the terminal equipment shown in Fig. 5 in the circuit from positive battery through the marking or left-hand contacts of relay 2|0, resistance 2 |5, line 2 Il, upper winding of relay 232, upper break contacts of relay 230, to negative battery through the upper winding of relay 226.

Relay 232 in operating interrupts the circuit through the upper winding of relay 223. When the circuit of the upper winding of relay 233 is interrupted by the operation of relay 232 to its right-hand or marking position, condenser 253 starts to discharge through the upper winding of relay 233. The constants of the upper winding of relay 233, resistance 25| and condenser 25D are so arranged that the discharging current of condenser 25|! is su'cient to maintain relay 233 in its right-hand position for approximately .2 of a second. At the end of about .2 of a second this discharge current falls to such a value that the current owing through the lower winding of relay 233 overpowers it and causes the armature of relay 233 to move to its left-hand position. In the left-hand position of the armature of relay 233 a circuit is completed for the operation of relay 221 from ground through the lefthand contacts of relay 233, lower outer break contacts of relay 235, break contacts of relay 228 to battery through the winding of relay 221. Relay 221 in turn completes a locking circuit from ground through its center set of lower operated contacts, the break contacts of relay 228, to battery through the winding of relay 221.

Relay 221 in operating completes a circuit for the operation of relay 225 from ground through the lower inner make contacts of relay 221, lower break contacts of relay 2|| to battery through the winding of relay 225. Relay 225 in operating completes an obvious circuit for lighting the answering lamp 224 associated with jack 223.

Relay 221 in operating transfers the lower or biasing winding of relay 226 from positive battery to the armature of relay 220 and prepares relay 226 for receiving telegraph signaling impulses from a subscribers station.

Relay 221 in operating also completes a circuit for the operation of relay 234 from ground through its lower outer make contacts, lower inner break contact of relay 235 to battery through the winding of relay 234. Relay 234 in operating connects battery to condenser 252 and the upper winding of relay 233. This charges condenser 25B to battery potential and causes the armature of relay 233 to move to its righthand position where a circuit is completed for the operation of relay 235 from ground through the right-hand contacts of relay 233, lower contacts of relay 234, upper inner break contacts of relay 230 to battery through the winding of relay 235.

Relay 235 in operating interrupts the operating circuit of relay 234 which releases. Relay 235 in operating completes a locking circuit from battery through its winding and inner lower make contacts to ground through the lower outer operated contacts of relay 221. Relay 235 in operating also transfers the circuit of the upper winding of relay 233 to marking contact of relay 232. Inasmuch as relay 232 is now in its marking position a circuit is completed for maintaining relay 233 in its right-hand position from ground through its upper winding, the upper inner operated contacts of relay 235 to battery through the marking contacts of relay 232.

Operator answers The operator at the central station, noting lamp 224, will answer and insert plug 83 in jack 223 or a jack in multiple with jack 223 in case jack 223 is multipled before a number of operators. It is to be understood that long multisection subscribers line circuits in accordance with this invention may be used equally well with many different types of switchboards and switching equipment at the central station including both single section and multisection switchboards. In case the switchboard is provided with a number of sections, both lamp 224 and jack 223 may appear before a number of operators. If this is the case, the rst operator to answer will und the circuit idle and Will insert the plug 83 in jack 223, The other operators, if they start to answer the call, will iind that the jacks in multiple with jack 223 will test busy so that they know that the call has already been answered.

When the operator inserts plug 83 in jack-223 a circuit is completed for the operation of relays 2| of terminal equipment and relay'84 of the cord circuit in series in a circuit from battery through :windingof relay 84, sleeve of plug 83 and jack 223 to ground through the Winding of relay 2| I. The operation of relay 84 completes an obvious circuit for the operation of relay 92 and conditions the cord circuit and extends the tip of the cord to the armature of relay 9| which is maintained on its marking contact at this time due to the operation of relay 92. If the operator has the printing key 89 associated with this cord circuit operated, the transmission circuit extends from the tip of plug 83 and operated upper contacts of relay 84 through the operators circuit equipment and upper Winding of relay 90 to the armature of relay 9|.

In the terminal circuit relay 2|I in operating vinterrupts the operating circuit of relay 225 which in turn releases and extinguishes the lamp 224. Relay 2| I in operating extends the transmission circuit from the tip of jack 223 through the upper winding of relay 220 to the armature of relay 226. Current iiowing through this transmission circuit from negative battery connected to the mark ing contacts of relay 226 through the upper winding of relay 220, upper contacts of relay 2| I, tip of jack 223, tip of plug 83, upper make contacts of relay 84, upper contacts of relay 88, operators equipment, upper contacts of relay 88. upper winding of relay 90 to positive battery through the amature and marking contacts of relay 9| causes relay 220 `to be operated to its marking icontact.

Relay 220 in operating to its marking contacty causes relays 2|2 and 2I3 to be operated to their marking contacts in a circuit from positive battery through the upper windings of relays 2 I2 and 2|3, resistance 2| 4, line 2| 8 to negative battery through the marking contacts of relay 220. Curernt owing through the upper windings of relays 2I2 and 2I3 overpowers current flowing through the lower windings of these relays causes. the armature of these relays to be operated to their marking positions. The operation of relays 2I2 and 2|3 to their marking positions transmits a marking condition over line 201 to the terminal repeater A at the intermediate station.

'I'he armature of relay 208 responds to this marking condition and moves to its marking position and completes the operating circuit of relay 54 described above since now negative battery is connected to one winding't'erminal and positive battery from the marking contacts of relay 208 to the other winding terminal of relay 54.

Relay 54 in operating completes a locking circuit from battery through its winding and upper break contacts to ground through the lower outer contacts of relay 53. Relay 54 in operating also completes an obvious circuit for the operation of relay 55.

Relay 55 in operating transfers the circuit of the lower winding of relay 58 from positive battery to the armature of relay 59. Relay 55 in operating also completes a transmission circuit from negative battery through the upper winding of relay 53, the upper operated contacts of relay 55, upper operated contacts of relay 53, line |90, resistance 206 to the armature and contacts of relay 258. These circuits condition relay 58 for responding to telegraph signal impulses.

The circuits are now in condition to enable the subscriber to communicate with the opera tor and indicate the other subscriber with Which he wishes to be connected. The operator will then complete the call by inserting calling plug |8| into a jack associated with the calling line. In case the called subscriber is connected to the central station by local line calling plug IliI will be inserted into the subscribers jack |39. It is to Ibe understood, however, that the called subscriber may be located a distance from the central exchange, whereupon the calling plug would be inserted into a jack similar to jack 223. If the called subscriber is located at a still greater distance and associated with a different exchange, the calling plug IUI would be inserted in the trunk circuit extending to that exchange, Where a second operator would complete the circuit to thecalled subscriber.

The long multisection subscribers line circuits described herein operate inthe same manner when connected to all of these different types of called subscribers circuits. Hence, this description of typical local subscribers line yand station equipment will illustrate the features of the long multisection subscribers line circuits. Assume, then, that plug |9I is inserted in jack |39. This completes a circuit for the operation of relays 98 and |40 in series from ground through the Winding of relay |40, sleeve of jack |39 and plug I0! to battery through the winding of relay 98. These relays operate and extend the transmission circuit to the subscribers station.

When the operator desires to call the subscriber she will operate ringing key |00 which connects ringing current over the tip of calling plug IOI and jack |39, the upper operated contacts of relay l4, upper winding of relay I4| to ground through condenser |46 and the winding of ringer |45 and the upper break contacts of relay 244.

The operation of relay |40 completes a circuit for the operation of relay |4| from negative battery through the lower winding of relay I4 I, operated lower make contacts of relay |40, T lead to the subscribers station, lower contacts of relay 244 to ground through the upper contacts of relay 244. Relay I4I in operating connects ground through its lower contacts to the ring of jack |39 and plug ISI and causes relay 91 to operate. Relay 91 in operating completes an obviouscircuit for lighting lamp |02. Y

When the subscriber answers by operating key 243, a circuit is completed from source of power |52 through the lower contacts of switch`243 and the winding of relay 244 to ground for the operation of this relay. p

Relay 244 in operating removesA the ground connected to the T lead and to the winding of ringer |45 and extends the line circuit from the R lead, upper operated contacts of relay 244, the normal contacts of recall key 231, transmitting contacts |51, send-receive and V break contacts |56 and lower winding of relay |55 to the T lead.

Relay 244 in operating and removing ground from the T lead interrupts the operating circuit through the lower winding of relay I4| and completes the line circuit through both windings of relay I4I. These windings are connectedso that the current nows through them in opposition and produces substantially no magnetic eiect on the relay. This permits the relay to release, which in turn interrupts the operating circuit of relay 91. The release of relay 91 extinguishes the light |02. Under these circumstances, the communication path between the subscribers station circuit, shown in Fig. 2, and the subscribers station circuit, shown in Fig. 8, is completed.

Transmission circuit The subscriber shown in Fig. 2 may operate his station equipment in a number of different ways. The subscribers station shown in Fig. 2 is provided with both a keyboard transmitter and a tape perforator and tape controlled transmitter. It is to be understood, however, that any suitable subscribers station equipment may be employed at the end of the long multisection line. The equipment at the intermediate point is arranged to work with all the different subscribers station circuits usually employed at local stations. For example, the distant subscribers station may be provided with the equipment shown at the subscribers station illustrated in Fig. 8. The arrangement shown in Fig. 2 illustrates that the subscribers station may provide all the services provided for a local subscriber.

In case it is desired to employ only the keyboard transmitter, the switch 33 is operated to the K position where it interrupts the circuit through the lower contacts. This interrupts the circuit through the start magnet 4I of the tape control transmitter distributor I1. In order to transmit, the subscriber must also operate the send-receive switch 20 to the position shown so the transmission circuit extends through the transmitting contacts I9. When the subscriber operates the keyboard, transmitting contacts I9 transmit telegraph signaling impulses in accordance with the keys operated by the subscriber by opening and closing the line to the intermediate point.

The line relay 24 at the subscribers station will follow the signal impulses and repeat them to the printer magnet 32 which records the transmitted signals on the local teletypewriter and provides a home copy for the subscriber. Relay 24 in its spacing position connects resistance 48 between the positive and negative terminals of the motor generator 29 to compensate for the load of the printer magnet 32 and thus maintain the load on the motor generator substantially constant and so the voltage output of the motor generator remains substantially constant when relay 24 is in both its marking and spacing positions.

In case the subscriber wishes to perforate tape at the same time the message is transmitted from the keyboard, key 33 is operated to the T-K position so that the lower contacts of this key are closed. This completes a circuit from the positive terminal of the motor generator through the lower contacts of key 33 to the cam pulsing contacts 35. These cam pulsing contacts are controlled by the cams which actuate transmitting contacts I9. Thus during each rotation of the cams controlling transmitting contacts I9 during which the impulses representing a particular character are transmitted, the cam pulsing contacts 35 are closed once. When these cam pulsing contacts are closed a circuit may be traced through them for the operation of the tape perforating magnet 36 from the positive terminal of motor generator 29, lower contacts of key 33 and cam pulsing contacts through the winding of perforator magnet 36 to the negative terminal of motor generator 29. This causes perforator magnet to operate and perforate a series of holes in the tape in accordance with the particular key depressed. The depression on the key mechanically controls and determines in what positions holes will be perforated in the tape when perforator magnet 36 operates.

Where the subscriber wishes to transmit from the keyboard, it is essential that the transmitter distributor switch 8| remain open so that the brush arm 43 of the distributor I1 will remain at rest and not interfere with the transmission from the transmitting contacts I9.

Means is also provided for permitting the subscriber to perforate tape and then transmit from the perforated tape. In case the subscriber wishes to merely perforate tape, he operates key 12 to the test position and leaves it in this position. With key 12 in test position, the power supply circuit is closed, as described above for the subscriber originating a call. However, in this case the line circuit extending to the intermediate station, shown in Fig. 3, is interrupted and remains open so that the equipment at the intermediate station as well as at the central station remains in its idle condition.

In case a subscriber wishes to secure a printed copy of his message at the same time that he perforates the tape he will leave key 33 in its center or T-K position. The operation of the equipment at the subscribers station with the keys in these positions is substantially the same as described above when messages were transmitted from the keyboard and a record of them simultaneously printed on the teletypewriter and perforated in the tape except that now no signals are transmitted over the line to the central station because key 12 has been operated so that it does not connect the transmitting equipment to the line but instead establishes a local circuit through the transmitting contacts and the line winding of the receiving relay 24.

The printed copy of the message perforated in the tape may be used for editing and correcting purposes so that the message may be edited before it is transmitted.

In case a subscriber merely wishes to perforate the tape without transmitting it and without securing a printed copy of it at this time the subscriber will operate the perforator control key 33 to its 'I' position in addition to operating key 12 to its test line position. The operation of key 33 to its T position closes all of the contacts of this key. In this position a mechanical connection between key 33 and the cams controlling the transmitting contacts I9 functions to prevent the operation of these transmitting contacts I9. Consequently, the cam pulsing contacts are unable to operate for each depression of a key. Instead, the U-bar contacts 34 are employedV These contacts operate every time a key is depressed but are disconnected unless key 33 is in the T position. These contacts cause the perforator magnet 36 to operate every time a key is depressed. It should be noted that the release of the perforator magnet 39 causes the tape to advance so that it will be in position to receive perforations representing the next character.

Under these conditions the line relay 24 and printer magnet 32 are maintained in their marking position in a circuit from the positive terminal of motor generator 29 through operated contacts of key 12, normal contacts of recall key IE5, upper winding of relay 24, transmitter distributor l1, break contacts I8, transmitting contacts I9, operated contacts of key 12 to the negative terminal of motor generator 29. Inasmuch as transmitting contacts I9 do not function at this time no copy of the symbols recorded on the tape will be printed on the teletypewriter. This necessitates the use of a counter to count the characters transmitted in each line. The counter is operated by magnet 31 which is energized in a circuit from negative terminal of motor generator 29 through the winding of counter magnet 31, counter contacts 19, upper contacts of key 33 and U-bar contacts to the positive terminal of motor generator 29. Thus every time the U-bar contacts are operated by the operation of one of the keyboard keys, counter magnet 31 is operated to count the character. However, in case a shift or unshift signal or certain other signals are transmitted, the lever 80 moves in the direcion indicated and mechanically operates the counter contact 19 so as to interrupt the circuit of the counting magnet 31 since these particular signals do not cause any character to be printed on the teletypewriter. At the end of the line counter contacts 19 are operated by lever 11 in response to a carriage return signal and cause the operation of release magnet 38 which restores the counter to zero.

Details of the arrangement of the equipment at the subscribers station and the mechanical. connections between the various parts is more fully described in U. S. Patents 1,965,572, granted July 10, 1934, to Burcky et al.; 1,965,602, granted `July lO, 1934, to Lake; and 1,969,891, granted August 14, 1934, to Lake et al.

The counter light 40 is provided which may be energized by closing the lamp control switch 39 and serves to illuminate the counter dial.

In this way, a supply of tape may be perforated without transmitting the information over the line to the central oice. If it is desired to return the equipment to normal without transmitting the information at this time key 12 is moved from the test position through the line position to the stop position and then to the normal or line position. This interrupts the locking circuit of relay 21. Relay 21 in releasing restores the apparatus at the subscribers station to its normal or'idle condition. It is to be noted that the equipment at the subscribers station cannot be deenergized so long as key 12 is in the test position. This arrangement tends to prevent the subscriber from leaving his equipment unattended with key 12 in the test position.

When it is desirable to transmit from the tape, the transmission circuit is established as described above, and key 12 returned to its normal or line position without first being operated to the stop position. Key 33 is operated to T position and switch 8| closed. This completes a circuit from the negative terminal of motor generator 29 through the tape control contacts 46, switch. 8l, winding of start magnet 4|, sendreceive contacts 29 and lower contacts of key 33 to positive terminal of motor generator 29. Start magnet 4l operates in this circuit and withdraws the stop latch 42 from engagement with the brush arm 43 carrying brush 44. This brush arm is driven through a friction clutch (not shown) from motor 33. As the brush arm 43 carries brush dd over the segments of distributor l1, the line circuit extending to the central oflice is interrupted in accordance with the perforations of tape 41 under the tape control contacts So long as the supply of perforated tape is available, tape control contacts 46 remain closed and the transmitter distributor continues to transmit over the line to the intermediate station. During this transmission relay 211, which is in series with the line, as described above, follows the signals vtransmitted by the distributor I1 and repeats them to the printer magnet 32 of the teletypewriter where they are recorded.

It is also possible for the subscriber to perforate additional tape at this time by the operation of the keyboard. The perforation of the tape at this time is just the same as described above when no signals were transmitted from the subscribers station..

In case the supply of perforated tape 41 becomes exhausted, the tape control contacts 'i6 will open and interrupt the circuit of the magnet 4l which will in turn release latch 42. Latch l2 will then engage the brush arm 43 and interrupt the transmission over the line to the intermediate and central stations.

It should be noted that telegraph signal impulses are transmitted from the subscribers station over the line extending to the intermediate station, shown in Fig. 3, as impulses of current and no-current, independently of how or what equipment is used to transmit the impulses. Relay 51 at the intermediate station does not respond to these impulses, since they pass through both windings of the relay in opposite directions. Relay 59, however, responds to the impulses transmitted from the subscribers station and repeats them to relays 293 and 29! in the circuit extending through its contacts, the

break contacts of relay 13, the innermost lower operated contacts of relay 53, line I9I, resistance 205 and upper windings of relays 293 and 291.

Relay 56 follows the signals repeated by relay 59 in a circuit from the contacts of relay 59 through the winding of relay 59 to ground through the upper operated contacts of relay 52. In response to spacing impulses transmitted by relay 59, relay 56 is operated to its right-hand position and in response the marking impulses transmitted by relay 59, relay 56 is operated to its leftwhand position. In the left-hand position relay 56 completes a circuit from ground through the outer upper operated contacts of relay 52, contacts of relay 56 to battery through the upper winding of relay 69. Relay 65 is maintained in its right-hand position by current flowing in this circuit. When relay 58 is operated to its right hand position it interrupts this circuit. Condenser 6I then starts to charge from battery through the upper winding of relay 60. The constants of the condenser 6i, resistance 62 and relay windings are so chosen that this charging current of the condenser 9i will maintain relay B in its right-hand position for approximately .3 second. During the normal transmission of signaling impulses over the system, relay 59 will not remain in its spacing position for .3 second before moving to its marking position. When relay 55 moves to its marking position it immediately discharges condenser 8| so that the .3-second interval will start again when relay 55 moves to its spacing position. Consequently, relay 69 will rel main in its right-hand position throughout the interrupts the circuit through the upper winding winding of relay 233 and upper inner operated contacts of relay 235 to battery through the marking contacts of relay 232. This permits condenser 25S to start to discharge through the upper winding of relay 233. However, as described above. the discharge current of condenser 250 owing through the upper winding of relay 233 will maintain the armature of relay 233 in its right-hand position for approximately .2 second. However, during the normal transmission of telegraph signal impulses, relay 232 will not remain in its spacing position for .2 second. V/hen relay 232 moves to its marking position before the termination of the .2-second ininterval it immediately recharges condenser 250 and completes the holding circuit for relay 233. Consequently, relay 233 will remain in its rightliand position throughout the transmission of signal impulses from the subscribers station shown in Fig. 2.

Relay 225 repeats the signal impulses over the transmission circuit extending from its contacts through the upper winding of relay 220, upper' operated contacts of relay 2||, resistance 222, tip of jack 223 and plug 83, contacts of relays 84 and 88 to the upper winding of relay 90 and thence to the armature of relay 9|. Relay 90 repeats the signal impulses to the transmission Vcircuit extending to the subscribers station circuit shown in Fig. 8, from the contacts of relay 90 through the upper winding of relay 9|, the upper break contacts of relay 95 and inner upper operated contacts of relay 88, normal contacts of ringing key |00, tip of plug and jack |33, the upper operated contacts of relay |40, the upper winding of relay |4|l, the R lead to the subscribers station, upper operated contacts of relay 244, normal contacts of recall key 231, transmitting contacts |51, break contacts of the send-receive and break contacts I 56, lower winding of relay |55, T lead to the line circuit at the central station and lower operated contacts of relay |40 to battery through the lower winding of relay lAil, The line relay |55 at the subscribers station responds to these signal impulses and repeats them to the printer magnet |54 of the teletypewriter 245. Thus the teletypewriter 245 records the signals transmitted from the distant subscribers station shown in Fig. 2.

In case the operator has the printing key 89 operated, relay 88 will be operated, in an obvious circuit. With relay 88 operated, the transmission circuit extends from the tip of plug 83, through operated contacts of relay B4, the operated contacts of relay 88, and the operators position circuit to the repeating relays 90 and 9| of the cord circuit. This'circut through the operators position circuit may be traced from the inner upper make contacts of relay 88, lower normal contacts of relay H6, normal contacts of relay H4, lower normal contacts of relay |24, lower winding of the line relay |04, transmitting contacts 242 of the operators teletypewriter, normal contacts of toll ringing key |09, normal contacts of relay ||5, to the upper outer operated contacts of relay 88. Splitting keys ||2, H3 and associated relays and ||4 are provided to enable the operator to communicate with either subscriber without communicating to the other subscriber.

Signal impulses are transmitted, either from the subscribers station shown in Fig. 8 or from the operators equipment shown in Fig. '1 to the outlying subscribers station shown in Fig. 2,

of relay 233 from ground through the upperover the same circuits between the operators circuit and plug 03 and also between the subscribers circuits shown in Fig. 8 and plug 83, described above for transmission from lthe subscribers station shown in Fig. 2 to these respective teletypewriters. In case the transmitting contacts 242 of the operators teletypewriter |03 or |51 of the subscribers teletypewriter 245 are operated to transmit the impulses, relay 220 of the terminal circuit shown in Fig. 5 repeats the impulses over line 2| 8 to relays 2|2 and 2|3 of the terminal repeater B. These relays in turn repeat the impulses over line 201 to the terminal repeater A at the intermediate station. I-Iere relay 208 repeats the impulses through resistance 205, line |90, the upper operated contacts of relay 53, upper operated contacts of relay 55 and upper winding of relay 58. Relay 58 follows the signals and repeats them to the subscribers line. At the subscribers station relay 24 follows the signals and repeats them to the printer magnet 32 of the subscribers teletypewriter which records the signals.

Break signals In case it is desired to interrupt the transmission being received at the subscribers station shown in Fig. 2, break key I8 is operated. This breek key is associated with the send-receive key 20 so that it is necessary to operate the sendreceive key first before the break key I8 can be operated. This merely short circuits the transmitting contacts I9 and interrupts the circuit of start magnet 4|. However, since transmission is being received at the station shown in Fig. 2 at this time, the operation of the sendreceive key performs no useful function at this time. Break key |3 in operating, however, interrupts the line circuit extending to the intermediate station. This causes relay 59 at the intermediate station to move to its spacing position. This repeats the spacing impulse over the transmission circuit, as described above, and also causes relay 56 to operate to its spacing position. In this case, however, relay ,55 will remain in its spacing position longer than the .3-second period required for relay 60 to operate to its left-hand position. At the end of the .3-second interval, relay 60 operates to its left-hand position and completes a circuit for the operation of relay 13 from battery through the winding of relay 13, the lower outer make contacts of relay 52 to ground through the left-hand and armature contacts of relay 60. Relay 13 in operating transfers the transmission path over lead |9| from the contacts of relay 50 to a source of 20-cycle ringing current 15 through a protective lamp 16. Relays 203 and follow the ringing current and transmit alternate impulses of marking and spacing currents of substantially a single unit in length. Relay 2||| at the central station repeats these impulses to the terminal circuit shown in Fig. 5.

When the break signal is originally received by the equipment shown in Fig. 5, relays 232 and 225 respond by moving to their spacing positions. Relay 228 repeats the break signal either to the operator or the subscribers station circuit shown in Fig. 8. Relay 232, however, will remain in its spacing position over .2 second in this case and permit condenser 250 to become sufliciently discharged to allow relay 233 to operate to its lefthand position. Relay 233 in operating to its left-hand position completes a circuit for the operation of relay 229 from ground through the left-hand contacts of relay 233, the lower operated contacts of relay 235, the lower normal contacts of relay 23| to battery through the upper winding of relay 229.

Relay 229 in operating removes the short circuit from its lower winding so that current may now ow from ground through the lower winding, resistance 249, the upper operated contacts of relay 235 to battery through the spacing contact of relay 232. Current flowing through this Winding tends to maintain relay 229 operated.

Relay 229 in operating also completes an obvious circuit for the operation of relay 230. Relay 230 in operating completes a circuit for the operation of relay 234 from ground through its lower contacts, upper break contacts of relay 23|, to battery through the winding of relay 234.

Relay 234 in operating completes a circuit through its upper contacts for charging condenser 250 and for operating relay 233 to its right-hand jposition. In the right-hand position the armature of relay 233 completes a circuit for the operation of relay 23| from ground through its armature and right-hand contacts, the lower operated contacts of relay 234, the inner upper operated contacts of relay 230, to battery through the winding of relay 23|. Relay 23| in operating interrupts the operating circuit of relay 234 and completes a locking circuit from ground through the lower operated contacts of relay 230, upper operated contacts of relay 23| to battery through the winding of relay 23|. Relay 234 in releasing interrupts the circuit through the upper Winding of relay 233, whereupon condenser 250 again starts to discharge.

However, ringing current transmitted by the operation oi relay 13 is received by relay 232 before the end of the second .2-second interval. Relay 232 follows the ringing current and during alternate half cycles, connects ground to the upper winding of relay 233 and fully charges condenser 250. This prevents relay 233 from moving to its left-hand position at this time. During the half cycles during which relay 232 is connected to its spacing contact it connects battery to the lower winding of relay 229 and tends to hold this relay in its left-hand position. Relay 232 at this time also tends to charge condenser 236 through resistance 249. During the half cycles during which relay 232 is not in its spacing position, condenser 235 will discharge through the lower winding of relay 229 and maintain this relay in its left-hand position.

It should be noted that when relay 230 operated it interrupted the transmission circuit to 'relay 226 so that this relay will remain in it spacing position and not receive or :follow the ringing current transmitted from the intermediate station.

It should be further noted that when the break signal is iirst received by relay 59, relay 59 operated to its spacing position during the next marking impulse transmitted by relay 58 to the subscribers station shown in Fig. 2. When relay 59 operates to itsv spacing position it reverses the bias current through the lower winding of relay 58 so thatit will tend to maintain relay 58 in marking position so long as the break impulses are received from the subscribers station. This insures the proper retransmission of the break signal to the central station and prevents the impulses being transmitted from a distant station yfrom interfering with the break signal.

it the central exchange relay 226 is operated which relay in turn repeats it to the subscribers station shown in Fig. 8. With relay 90 in its spacing position it is impossible for the subscribers station shown in Fig. 8 to transmit marking signal impulses so that the line relay |55 at this station will be operated to its spacing position and remain in this position independently of the operation of the transmitting contacts |51 at the subscribers station shown in Fig. 8. So long as the subscriber at the station shown in Fig. 2 maintains the break contacts I8 open, the circuits remain in the condition described above. should be noted that the reception ofl the break signal by the teletypewriter 245 at the subscribers station shown in Fig. 8 causes the send-receive contacts |56 to be operated so that the transmitting contacts |57 are short-circuited. However, these contacts are not operated sufciently to interrupt the line circuit through the lower Winding of relay |55.

When the subscriber at station shown in Fig. 2 restores break key |8 to normal the line circuit to the intermediate station is reclosed. This causes the armature of relay 59 to moveto its marking position, which in turn causes the armature of relay 56 to move to its marking position. Relay 56 in operating to its marking or left-hand position completes a circuit through the upper winding of relay 60, which causes its armatureto move to the right-hand position and interrupt the circuit through the winding of relay 13. Relay 13 releases, disconnects the source of ringing current 15 from the transmission circuit and connects the transmission circuit tocontacts of relay 59. This causes the transmission of the marking impulse over lead |9| to relays 203 and 20|. These relays in turn transmit a marking impulse over line 201 to the central station. This marking impulse is repeated over line 2|'| to relay 232. Relay 232 operates toits marking position and remains in this position.v In the marking position, relay 232 completes a circuit through the upper winding of relay 233 for maintaining the armature of this relay in its right-hand position. Relay 232 in remaining in its marking position interrupts the locking circuit of relay 229 and permits condenser 236 to discharge, after which relay 229 will be operated to its right-hand position by current flowing in an obvious circuit through its center Winding.

Relay 229 in operating to its right-hand position interrupts the circuit for relay 230. Relay 230 releases and in turn releases relay 23 Relay 230 in releasing reconnects the upper winding of relay 226 to lead 2|'|. Relay 226 is then operated to its marking position by the marking impulse received over lead 2|1. Relay 226 will repeat this marking impulse to the local subscribers station shown in Fig. 8, whereupon the transmission circuits are restored to their normal condition and the subscriber at station shown in Fig. 2 may now transmit over the system as described above.

If it is desired to interruptv the transmission from the subscribers station shown in Fig. 2 a break signal may be transmitted either by the operator or by the subscriber at the subscribers station shown in Fig. 8. This transmits a break or spacing signal over the tip of plug 83 to relay 220. Relay 220 operates to its spacing position .during the transmission of the first marking impulse by relay 226 after the reception of the break signal and retransmits the break signal over line 2|8 to relays 2|2 and 2|3. Relay 220 in operating to its spacing position reverses the bias current through the lower winding of relay 226. This causes relay 226 to remain in its marking position and prevents it from interfering with the break signal received by relay 220.

Relays 2 I2 and 2|3 repeat the break signal over line 291 to relay 208 of repeater A. Armature of relay 208 moves to its spacing position and repeats the break signal over line I 90 to relay 58. The armature of relay 58 in turn moves to its spacing position during the first marking impulse repeated by relay 59 after reception of the break impulse and repeats the break signal to the subscribers line. With the armature of relay 58 in its spacing position relay 59 is maintained in its marking position so that if any succeeding impulses are transmitted by the subscribers station they will not interfere with the break signal.

Relay 24 at the subscribers station responds to the break signal by moving to its spacing position and remaining there independently of the o-peration of the transmitting contacts I9 or of the impulses transmitted by transmitting distributor I1. This indicates to the subscriber that the distant subscriber wishes to interrupt the transmission. The teletypewriter also causes the sendreceive contacts 20 to be operated to the receive position at this time This interrupts the circuit of the start magnet 4| of transmitting distributor I1 which in turn interupts the transmission from distributor I1 had the subscriber been transmitting from tape. 'Ihe operation of the send-receive contacts 20 also short circuits the transmitting contacts I9 and thus prevents the subscriber from transmitting from the keyboard until this switch has been again operated to the sending position.

Recall In case the subscriber at the station shown in Fig. 2 Wishes to recall the central exchange operator, the subscriber will momentarily operate recall key I6. This interrupts the line circuit at the subscribers station and connects ground to conductor I I from the operated contacts of recall key I6 and interrupts the circuit through the upper winding of relay 51 and connects ground to the circuit through the lower winding of relay 51. This circuit for the operation of relay 51 may be traced from ground through the operated contacts of recall key I6, the upper winding of relay 24, transmitting distributor I1, contacts of the break key I8, contacts of the transmitting device I9, contacts of the line test key 12, line I I, the inner upper operated contacts of relay 5I, lower winding of relay 51 to negative battery.

Relay 51 in operating completes a circuit for the operation of relay 10 from ground through the upper contacts of relay 50, contacts of relay 51 to battery through the winding of relay 1i). Relay 10 operates and interrupts the locking circuit of relay 5 I. Relay 5| thereupon releases and releases relay 52. Relay 52 in turn releases relay 53 which causes the release of relays 54 and 55. 'Ihe release of these relays restores the circuit to its idle condition. The release of relay 5| interrupts the operating circuit of relay 51 which in turn interrupts the operating circuit of relay 10. Relay 10, however, is made slow in releasing so that relay 5| will have sufficient time to fully release before the contacts of relay 10 reclose. This insures the release of relay 5| at this time.

of relay 232 responds to the spacing signal by moving to its spacing position. This causes the operation of relay 233 to its left-hand position after approximately .2 second. In the left-hand position relay 233 completes a circuit for the operation of relay 229 to its right-hand position.

Relay 229 in operating to its right-hand position removes the shunt from its lower locking winding so that it will lock in its left-hand position under control of the spacing contacts of relay 232. Relay 229 also causes the operation of relay 230. Relay 238 in operating interrupts the transmission circuit to relay 226 and also completes a circuit for the operation of relay 234. Relay 234 in operating completes a circuit for the operation of relay 233 to its right-hand position through its upper winding. Relay 233 in turn completes a circuit for Vthe operation of relay 23|. Relay 23| locks operated under control of relay 239 and interrupts the operating circuit of relay 234 which then releases. The operating circuits of these relays shown in Fig. 5 are the same as for a break signal described above. In. case of a disconnect signal, however, relay 232 will remain upon its spacing contact at this time, since no ringing current is transmitted over the system. This permits relay 233 to again operate to its left-hand position at the end of the second .2-second interval. In the left-hand position the armature of relay 233 completes a circuit for the op-eration of relay 228 from ground through the left-hand contacts of relay 233, lower outer operated contacts of relay 235, the lower operated contacts of relay 23| to battery through the winding of relay 228. Relay 228 in operating completes a locking circuit from battery through its winding and operated contact to ground through the middle set of lower contacts of relay 221.

Relay 228 in operating interrupts the locking circuit of relay 221 from battery through the winding of relay 221 and the break contacts of relay 228 to ground through the center set of lower operated contacts of relay 221. This permits relay 221 to release which in turn causes the release of relays 235, 228, 229, 239 and 23|. The release of these relays restores the circuit to its idle condition except that relay 2|| remains operated.

The release of relay 221 also connects ground through its inner lower break contacts to the ring of jack 223 and plug 83 which causes the operation of relay 85. The operation of relay 85 causes the supervisory lamp 86 to light. The operation of relay 85 also completes a circuit for the operation of relay 81 which locks operated through its upper contact.

When the subscriber releases the recall key it disconnects ground from line I I and completes the circuit between lines I0 and II. The apparatus at the intermediate station shown in Fig. 3 and the apparatus of the intermediate line sections shown in Fig. 4, as well as the terminal apparatus shown in Fig. 5 operate as described when the subscriber initiates a call. The operation of relay 221 in Fig. 5 at this time removes ground from the ring of jack 223 and plug 83. This permits relay 85 of the cord circuit to release. However, relay 81 remains operated until the operator operates the printing key 89. Until the operator operates this key, the interrupter 93 is connected to the circuit of the supervisory lamp 86 and causes this light to flash. When the operator operates key 89, relay 81 is released and this extinguishes the supervisory lamp 86.

In case the automatic recall features are not provided in the cord circuit, the supervisory lamp 86 will follow the operation of the recall key I5. At the subscribers station, recall signals may be sent by momentarily operating the line key 12 first to the stop position, then to the test position and finally restoring it to the line position.

The operation of key 12 to the stop position interrupts the locking circuit of relay 21 and permits this relay to release. The release of relay 21 disconnects the power supply from the motor generator 29 and motors 30 and 3| at the subscribers station. It also causes the release of relay I2. The release of relay I2 interrupts the line circuit to the subscribers station and connects ground to lead II which extends to the intermediate station shown in Fig. 3 in the same manner the operation of recall key I6 connects ground to this lead. This causes the circuits at the intermediate station and central office to operate as described above when the recall key was operated.

Usually recall key I 6 will only be provided when automatic recall is not provided at the central ofiice so that the subscriber can readily flash the supervisory lamp in the cord circuit at the cen- However, when the automatic recall feature is provided in the cord circuit, the recall key is not necessary and usually will not be provided because a single recall signal may be readily transmitted by line key 12.

However, it is to be understood that either or both of these keys may be provided when the cord circuit at the central oce is equipped to provide a ashing recall signal.

Disconnect When the subscriber has completed the transmission of the message he will operate the line key 12 to the stop position. This will deenergize the equipment at the subscribers station and connect ground to lead I I extending to the intermediate station just as described under Recall `except that the line key is returned to the line position instead of being operated to the test position after being operated to the stop position. The circuits at the intermediate station and the central exchange will operate as described under Recall excepting that the supervisory lamp 86 remains lighted and does not flash. The operator at the central exchange will then remove plug 83 from jack 223. This causes relays 84 and 2I| to release. Relay 2| I in releasing interrupts the transmission circuit through the upper winding of relay 220 so that the armature of this relay will move to its spacing position and transmit a spacing signal over line 2I8. This spacing signal is repeated by relays 2l2 and 2I3 over line 201. Relay 208 moves to its spacing position in response to this spacing signal. Relay 208 in moving to its spacing position at this time performs vno useful function since the circuits have all returned to their normal or idle position. Y

A disconnect signal may be transmitted from the outlying subscribers station in response to a motor stop signal transmitted from the subscribers station or received by this station. The motor stop signal operates contacts |5 which interrupt the locking circuit of relay 21 in the same manner that key 12 interrupts this circuit and permits relay 21 to release. The circuits then function and are returned to normal as described above.

Operator calls When the operator desires to call the outlying subscribers station shown in Fig. 2, she will insert calling plug IOI in jack 223. Of course the answering plug 83 of the cord will usually be inserted in the jack similar to jack |39 of the line to the calling subscribers station. When the calling subscriber desires to communicate with the subscribers station shown in Fig. 2, as pointed out above, the calling plug |0I is inserted in jack 223. This causes the operation of relays 2II and 98 in series. The operation of relay 2II completes a transmission circuit from the tip of plug 59S through the winding of relay 220 to the contacts of relay 226. This causes the armature of relay 228 to operate to its marking contact and t0 transmit a marking signal over line 2|8. This signal is repeated by relays 2I2 and 2I3 over line 201y to the intermediate station. At the intermediate station the armature of relay 208 responds by moving to the marking contact. I-Iowever, this performs no useful function at this time.

When the operator inserts calling, plug IOI in jack 223 as described above, a circuit is completed for the operation of relay 91 from ground through the lower inner break contacts of relay 221, ring of jack 223, ring of plug IOI to battery through the winding of relay 9,1. Relay 91 in operating completes an obvious circuit for lighting the supervisory lamp |02.

The operator will then operate ringing key |00 in the cord circuit.V This applies ringing current to the transmission circuit through .the upper winding of relay 220. Relay 220 will follow the ringing current and transmit alternate impulses of marking and spacing current of substantially unit length over line 2I8. Relays 2I2 and 2I3 repeat these impulses over line 201. Relay 208 of the intermediate station in turn repeats these impulses over line |90.

Alternating current relay 63 responds to these impulses. Condenser 64 is alternately charged and discharged through the windings of relay 63 from theV positive and negative batteries connected to the contacts of relay 208 over a circuit extending from the armature f relay` 208, resistance 206, lead |90, upper break contacts of relay 53 to the condenser 64. The same terminal of condenser 64 is also connected to negative battery through resistance |59. This resistance tends to charge or discharge condenser 64 during the time the armature of relay k208 is passing from one contact to the other. Relay 63 is an alternating current relay and tends to operate and remain operated so long as these impulses are received.

Relay 63 in operating completes an obvious circuit for the operation of relay 65. Relay 65 in turn completes a circuit for the operation of relay 60 to its right-hand position from ground through -the upper operated contacts of relay 65, lower break contacts of relay 66 to battery through the upper winding of relay 60. Current ilo-wing in this circuit opposes and overcomes the current ilowing through the lower winding of relay 66 so that relay 69 will operate to its righthand position. With the armature of relay 60 in its right-hand position a circuit is completed for the operation of relay 66 from ground through |19 is connected to line lll.

the varmature and right-hand contacts of relay 60, the lower break contacts of relay 52 to battery through the winding of relay v66. Relay 66 in operating completes a locking circuit from battery through its winding and inner upper operated contacts to ground through the inner upper operated contacts of relay 65. Relay 66 in operating interrupts the operating circuit of relay 60 so that relay 60 starts to release at this time. However, condenser 6| starts to charge through the upper winding of relay 60 at this time. The charging current of this condenser is sufcient to maintain relay 60 in its right-hand position for approximately .3 second in the preferred embodiment of this invention. At the end of this time interval, relay 60 will be operated to its left-hand position by current flowing through its lower winding in an obvious circuit. With the armature of relay 60 in its left-hand position at this time a circuit is completed for the operation of relay 61 from ground through the armature and left-hand contacts of relay 60, lower break contacts of relay 52, upper operated contacts of relay 66 to battery through the winding of relay 61. Relay 61 in operating completes an obvious circuit for the operation of relay 68. The operation of relays 61 and 68 connects the source of 20-cycle ringing current 15 to line l0 extending from the subscribers station in the following circuit: from ground through the source of ringing current 15, protective lamp 16, inner operated contacts of relay 61, operated contacts of relay 68, middle set of normal contacts of relay 5|, line |0, condenser 23, ringer 22 at the subscribers station to ground through the contacts of key 12 and the inner break contacts of relay |2.

When the operator releases ringing key |00, ringing current is disconnected from the tip of plug |0| and marking potential is connected thereto. This causes a marking condition to be transmitted to the intermediate station. Relay 63 will not remain operated under this condition since condenser 64 will become fully charged. Hence, no current will flow through the winding of relay 63 so relay 63 will release and in turn release relay 65 which in turn releases relay 66. Relay 66 releases relay 61 which in turn releases relay 68. The release of these relays disconnects source of ringing current 15 from the line extending to the subscribers station. Relay 68 is slow in releasing. During its release time the capacity of the lines l0 and is charged to battery potential in a circuit from positive battery through resistance 18, break contacts of relay 61, operated contacts of relay 68, and break co-ntacts of relay 5|. Then when relay 68 releases relay Since the line is charged to battery potential, this relay does not falsely operate by any line charging current.

The above relays follow the operation of ringing key |00 in the cord circuit as described above. In addition, ringer at the subscribers station rings when the ringing key |00 in the cord circuit is operated. The subscriber answers in the same manner as when orginating a call by momentarily operating key 12 to the test position and then returning it to its normal or line position. This starts the equipment at the subscribers station and completes the line circuit at the subscribers station. During the next interval during which the operator has released ringing key |00 relays 49, 50, 5|, etc., at the intermediate station will operate as described above when a subscriber originates a call. When relay 221 of the terminal equipment shown in Fig. 5

operates in responseto thestarting of the-equipment at the subscribers station shown in Fig. 2,

it will disconnect ground from the ring of jack `221 and thus permit relay 01 to release. The release of relay -91 allows the supervisory llamp |02 to be extinguished. This indicates to the operator that the subscriber has answered so that the operator will not reoperate the ringing key to ring the subscriber. The subscribers may corninunicate between themselves and the operator at the central exchange, if necessary, as described above, and at the termination of the call, disconnect by operating the line key to the stop position for a short interval of time and then releasing it.

Unattended service In case it is desired to provide unattended service for the outlying subscribers station, condenser 2| and relay 25 are connected in parallel with the condenser 23 and ringer 22. In case the subscriber does not answer after the operator has rung bell 22 several times, the operator will hold ringing key |00 operated for at least ten seconds. This will apply ringing current to the subscribers line for a similar interval of time. Relay 25 will operate at this time and complete a circuit for the operation of relay 26 from source of power 26 through the winding of relay 26 and the contacts of relay 25 to ground. Relay 26 is slow to operate and does not close its contacts for at least six or eight seconds. Consequently, if ringing current is applied for nine or ten seconds continuously, so that relay 25 remains operated during this time, relay 26 will operate. Relay 25 in operating completes a circuit for the operation of relay 21 from source of power 28, winding of relay 21, contacts of relay 26 to ground. Relay 21 in operating locks operated and energizes the equipment at the subscribers station, as described above when the subscriber initiates a call. lay 2 is also operated when relay 21 operates and completes the line circuit through the subscribers station. Then when the operator releases the ringing key after approximately ten seconds, relays 63, 65, 66, 61, and 68 release whereupon, if the equip-ment at the subscribers station has responded as described above, relays 49, 50, 5|, 52, etc., operate asy described when the subscriber initiates a call. These relays in turn eventually cause relay 221 of the terminal equipment shown in Fig. 5 to operate. The operation of relay 221 removes ground from the ring of jack 223 which in turn permits relay 91 to release and in turn extinguish the supervisory light |02 which indicates to the operator that the subscribers equipment is in condition to receive signaling impulses. The operator will then notify the other subscriber who can transmit the desired message to the outlying subscriber. At the termination of the message it is necessary to transmit a motor stop signal to the subscribers station shown in Fig. 2. This motor stop signal operates the motor control contacts |5 through the teletypewriter equipment. The operation of the motor control contacts interrupts the locking circuit of relay 21. 'Ihis relay then releases and restores the circuit to its idle condition which in turn causes the circuit of the intermediate station and central station to operate as described above under Dlsconnect.

If the subscribers equipment did not become energized before the operator released ringing key |00, the supervisory lamp |02 in the cord circuit would remain lighted because relays 49, 50, etc.,

would not operate when relays 63, 65, 66, 61 and 68 released. The operator would then again attempt to start the subscribers equipment by holding the key Elli) operated for a long interval of time. The circuits would then again operate as described above.

It is to be understood that the foregoing description describes certain typical circuits, including the subscribers station circuits and the central station circuits. However, it is to be understood that the circuit arrangement at the intermediate point will cooperate With other types of subscribers station circuits such as commonly employed in telegraph systems. Also, the terminal equipment at the central exchange may be arranged to cooperate with any suitable type switching equipment, including various types of single-section and multisection switchboards as well as with machine switching circuits. It is to be further understood that the invention dened in the claims appended hereto is not limited to the specific circuit arrangement at the intermediate point or central office nor to the specific time intervals described.

What is claimed is:

l. In a telegraph exchange system a long subscribers line circuit comprising subscribers station equipment, an intermediate repeater station, central interconnecting station equipment, terminal equipment connected to said long subscribers line circuit at said interconnecting station, a telegraph line connecting said subscribers station and said intermediate station, a full duplex channel connecting said intermediate station and said central station, means at said subscribers station for continuously controlling supervisory signals at said central station comprising means for transmitting a series of signals of alternate character and of uniform length from said intermediate station during break signals which exceed the length of spacing signals encountered in transmitting code combinations of telegraph signaling impulses.

2. A method of supervising over a long multisection subscribers line circuit which comprises transmitting a break signal over the intermediate sections of said system for a short interval of time in response to a break signal transmitted from the subscribers station and then transmitting a series of uniform length impulses of alternate character over the intermediate sections during the remainder of the break signal transmitted from the subscribers station.

3. A telegraph exchange'system comprising a central interconnecting station, a plurality of local subscriber stations, lines connecting said subscribers stations to said central station, interconnecting means at said central station for interconnecting said local stations, a distant subscribers station, telegraph equipment similar to the telegraph equipment at said local stations located at said distant station, an intermediate repeater station, a line connecting said distant subscribers station to said intermediate station, a full duplex telegraph channel connecting said .intermediate station and said central station, terminal equipment located at said central station connected to said full duplex channel for cooperating with said switching equipment in the same manner that said local station lines cooperate therewith, and means at said repeater station for transmitting ringing current over said intermediate line section in response to break signals which exceeds a predetermined short interval of time.

4. A method of distinguishing between break signals and disconnect and recall signals transmitted over an intermediate section of a long subscribers line which comprises the step of first transmitting said supervisory signaling conditions oVer said line and then applying ringing current to said intermediate section in response to one of said signals which exceeds a predetermined minimum interval of time.

5. In a telegraph system comprising a plurality of local subscribers stations, a central interconnecting station, telegraph lines connecting said subscribers station, means at each of said subscribers stations and said central station for transmitting and responding to at least three signaling conditions in addition to two signaling conditions employed for transmitting code combinations of telegraph signaling impulses, an outlying subscribers station and an intermediate repeater station, and apparatus located at said outlying subscribers station and said intermediate station for transmitting and responding to the same signaling conditions as transmitted between said local subscribers stations and said central station, a full duplex telegraph channel arranged to transmit only two dilerent signaling conditions connecting said intermediate station and said central station, and means for transmitting and receiving to all of said signaling conditions to and from said full duplex channel which comprises transmitting impulses of uniform length and of alternate character over said full duplex channel in response to one of said signaling conditions which exceeds a predetermined interval of time.

6. In combination, a first communication line circuit capable of transmitting three signaling conditions and a second communication line capable of transmitting only two signaling conditions, means for transmitting three signaling conditions in addition to code combinations of impulses of two of said signaling conditions over said first line circuit, and means for transmitting all -of said signal conditions over said second line circuit which comprises transmitting a series of impulses of uniform length and of alternate character over said second line in response to one of said signaling conditions transmitted over said first line circuit.

'7. A multisection subscribers line circuit comprising a subscribers station, an intermediate repeater station, a line connecting said subscribers station and said intermediate station, a central telegraph exchange station, a full duplex telegraph channel connecting said intermediate station and said central exchange station, means for transmitting signaling impulses of substantially unit length and of alternate character over said full duplex channel from said intermediate station to said central station in response to break signals exceeding a predetermined minimum period transmitted from said subscribers station, and means for transmitting a series of impulses of subtantially unit length and alternate character over said full duplex channel from said central station to said intermediate station to call said subscribers station, and means at said intermediate station for responding to said series of impulses and for applying ringing current to a line extending to said subscribers station in response thereto. 1

KARL E. FITCH. 

